Photography Terms Explained: Focal Length

When you’re a beginner starting out in the world of photography, it can sometimes be a little daunting due to the amount of photographic jargon banded about – so I’m going to start a new series of posts on LearningTheLight.com explaining various photography terms, in a non-technical, simple way (well, hopefully!).

I’m going to start by talking about ‘Focal Length’.

Left Photo: Short Focal Length, Right Photo: Longer Focal Length

Simply put, focal length refers to how long that particular lens ‘reaches’. So, a lens with a smaller focal length, such as 18mm, will have less of a reach – meaning your photos will include more of your subject, and probably your subject’s surrounding too. A longer focal length, on the other hand, such as 200mm, will mean your lens has more of a reach – so your photo will show more detail of your subject, and perhaps not be including much of your subject’s surroundings at all.

See the couple of photos above as an example. The photo on the left was taken using a short focal length, whilst the one on the right used a long focal length. See how the first image includes more of the subject? (in this case, the lovely model is my wife…). We can see her torso, from the waist up, as well as the trees and path behind her.

The image on the right, with the longer focal length, has more detail – it’s a lot more ‘close-up’; we can only see her head and shoulders.

Focal length is an important point to think about when you’re looking into getting a new lens, as, depending on what you will want to be shooting, different focal lengths are better for different things. For example, if you’re into wildlife photography, and you thus don’t want to be scaring the animals away by standing too close to them, you’ll want a lens with a very long focal length – such as 200mm, 300mm or even higher. These kind of long focal length lenses are classed as ‘telephoto’ lenses. See the photo I took of a squirrel below, using a long focal length of 171mm:

On the other hand, you may really be into shooting landscapes, and so you’ll generally wanting to be taking in as much of the scene as possible – so you’ll want a short focal length, perhaps something like an 18mm or even 14mm lens. These lenses are normally classed as ‘wide’ or ‘wide angle’ lenses. See the below example, which was taken at 18mm:

By using a short ('wide') focal length of 18mm, I was able to get all the family in on this shot

Focal length also has an effect on other things, such as how blurry the backgrounds in your photos look – basically, a longer focal length creates more background blur, whereas a shorter focal length creates less. See my ‘How To Blur The Background In Your Photos‘ guide for more info.

Lastly, lenses can either have varying focal lengths, called ‘zoom’ lenses – or they can have a fixed focal length, which are called ‘prime’ lenses. I’ll talk about both types in later ‘photography terms explained’ posts.

Anyway, hope that’s been of use! Let me know if you have any specific photography terminology that you’d like me to delve into for further posts in a comment below. I’m also on Twitter and Facebook if you’d prefer to contact me there.